Development Of Twin-twin Transfusion Syndrome Research Articles

Predicting Adverse Outcomes in Monochorionic-Diamniotic Twins: The Role of Intertwin Discrepancy in Middle Cerebral Artery Doppler Measurements and the Cerebroplacental Ratio.

This study was aimed to evaluate the role of intertwin discrepancy in middle cerebral artery peak systolic velocity (MCA-PSV) and cerebroplacental ratio (CPR) for the prediction of adverse outcomes in monochorionic-diamniotic (MCDA) twin pregnancies. A retrospective cohort study of MCDA pregnancies that underwent ultrasound surveillance at a perinatal referral center from 2007 to 2017. Intertwin MCA-PSV discrepancy (MCA-ΔPSV-MoM) was defined as the absolute difference of MCA-PSV multiple of the median (MoM) for gestational age between twins. Intertwin CPR discrepancy (CPR-Δ) was defined as the absolute difference of CPR between twins. The maximum MCA-ΔPSV-MoM and CPR-Δ before and after 26 weeks of gestation were assessed as predictors of pregnancy and neonatal outcomes through simple logistic regression models and Pearson's correlation coefficients. Receiver operating characteristic (ROC) curves were generated to determine the predictive value of maximum MCA-ΔPSV-MoM and CPR-Δ. A total of 143 MCDA pregnancies met inclusion criteria. There was a significant association between MCA-ΔPSV-MoM at <26 weeks and the development of twin anemia-polycythemia sequence (TAPS; p = 0.007), intrauterine fetal demise (IUFD; p = 0.009), and neonatal intensive care unit (NICU) admission (p < 0.05). MCA-ΔPSV-MoM at ≥26 weeks was associated with the development of TAPS (p < 0.001). CPR-Δ at <26 weeks was associated with the development of twin-twin transfusion syndrome (TTTS; p = 0.03) and NICU admission (p = 0.02). MCA-ΔPSV-MoM at ≥26 weeks was highly predictive of TAPS (area under curve [AUC] = 0.92). A cut-off of 0.44 would identify TAPS with 100% sensitivity and 73% specificity. In MCDA pregnancies, intertwin MCA and CPR discrepancies are associated with adverse pregnancy and neonatal outcomes, including TAPS, TTTS, IUFD, and NICU admission. Evaluation of intertwin MCA and CPR differences demonstrated the potential for clinical predictive utility in the surveillance of MCDA twin pregnancies. · Intertwin discrepancy of MCA-PSV and CPR is associated with adverse pregnancy outcomes.. · Intertwin differences in Doppler ultrasound may occur prior to meeting diagnostic criteria for TTTS or TAPS.. · There is potential clinical predictive utility in MCA and CPR surveillance of MCDA twin pregnancies..

Outcome of monochorionic twin pregnancy with selective fetal growth restriction at 16, 20 or 30 weeks according to new Delphi consensus definition.

To report the outcome of selective fetal growth restriction (sFGR) diagnosed according to the new Delphi consensus definition, and determine potential predictors of survival, in a cohort of unselected monochorionic diamniotic twin pregnancies. This was a retrospective study of monochorionic diamniotic twin pregnancies followed from the first trimester onward, which were diagnosed with sFGR at 16, 20 or 30 weeks' gestation. sFGR was defined according to the new Delphi consensus criteria as presence of either an estimated fetal weight (EFW) < 3rd centile in one twin or at least two of the following: EFW of one twin < 10th centile, abdominal circumference of one twin < 10th centile, EFW discordance ≥ 25% or umbilical artery pulsatility index of the smaller twin > 95th centile. The primary outcomes were the overall survival rate (up to day 28 after birth) and risk of loss of one or both twins. We further determined possible predictors of survival using uni- and multivariate generalized estimated equation modeling. We analyzed 675 pregnancies, of which 177 (26%) were diagnosed with sFGR at 16, 20 or 30 weeks. The overall survival rate was 313/354 (88%) with 146/177 (82%) pregnancies resulting in survival of both twins, 21/177 (12%) in survival of one twin and 10/177 (6%) in loss of both twins. Subsequent twin anemia-polycythemia sequence (TAPS) developed in 6/177 (3%) and twin-twin transfusion syndrome (TTTS) in 17/177 (10%) pregnancies. All TAPS fetuses survived. The survival rate in sFGR pregnancies that subsequently developed TTTS was 65% (22/34), compared with 91% (279/308) in those with isolated sFGR (no subsequent TAPS or TTTS) (P < 0.001). The majority of sFGR cases were Type I (110/177 (62%)) and had a survival rate of 96% (212/220), as compared with a survival of 55% (12/22) in those with Type-II (P < 0.001) and 83% (55/66) in those with Type-III (P = 0.006) sFGR. The majority of sFGR pregnancies (130/177 (73%)) were first diagnosed at 16 or 20 weeks (early onset), with a survival rate of 85% (221/260), as compared with a survival of 98% (92/94) in sFGR first diagnosed at 30 weeks (late onset) (P = 0.04). A major anomaly in at least one twin was present in 28/177 (16%) sFGR cases. In these pregnancies, survival was 39/56 (70%), compared with 274/298 (92%) in those without an anomaly (P < 0.001). Subsequent development of TTTS (odds ratio (OR), 0.18 (95% CI, 0.06-0.52)), Type-II sFGR (OR, 0.06 (95% CI, 0.02-0.24)) and Type-III sFGR (OR, 0.21 (95% CI, 0.07-0.60)) and presence of a major anomaly in at least one twin (OR, 0.12 (95% CI, 0.04-0.34)), but not gestational age at first diagnosis, were independently associated with decreased survival. Isolated sFGR is associated with a 90% survival rate in monochorionic diamniotic twin pregnancies. The subsequent development of TTTS, absent or reversed end-diastolic flow in the umbilical artery of the smaller twin and the presence of a major anomaly adversely affect survival in sFGR. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Fetal ventricular strain in uncomplicated and selective growth-restricted monochorionic diamniotic twin pregnancies and cardiovascular response in pre-twin-twin transfusion syndrome.

ABSTRACTObjectivesOur primary aim was to confirm whether intertwin discordance in ventricular strain and ductus venosus (DV) time intervals predicts twin–twin transfusion syndrome (TTTS). Secondary aims were to create gestational‐age ranges for ventricular strain in uncomplicated monochorionic diamniotic (MCDA) twin pregnancies without selective intrauterine growth restriction (sIUGR) and to characterize the relationship of ventricular strain with gestational age in MCDA twin pregnancies with sIUGR that did not develop TTTS.MethodsIn the period 2015–2018, we enrolled 150 MCDA twin pregnancies consecutively into this prospective, blinded study of global longitudinal left and right ventricular strain. With the observer blinded to twin pairing and pregnancy outcome, videoclips of the four‐chamber view, which had been recorded during ultrasound surveillance in the usual window for development of TTTS (16–26 completed gestational weeks), underwent offline measurement of strain. Uncomplicated MCDA twin pregnancies, without sIUGR, were used to test the association between strain, gestational age and estimated fetal weight using mixed‐effects multilevel regression. Inter‐rater reliability was tested in 208 strain measurements in 31 fetuses from pregnancies which did not develop TTTS and within‐fetus variation was assessed in 16 such fetuses, in which multiple four‐chamber views were taken on the same day. The effect of sIUGR on strain in otherwise uncomplicated MCDA twin pregnancy was analyzed. MCDA twin pregnancies were defined as ‘pre‐TTTS’ when, having been referred for TTTS evaluation, they did not satisfy Quintero staging criteria, but subsequently developed TTTS requiring laser treatment. MCDA pregnancies which did not develop TTTS comprised the ‘non‐TTTS’ group. Cardiovascular parameters measured in these cases included tissue Doppler parameters and DV early filling time as a percentage of the cardiac cycle (DVeT%). Intertwin strain and DVeT% discordance was compared between non‐TTTS and pre‐TTTS cases, matched for gestational age.ResultsPaired strain data were available for intertwin comparison in 127/150 MCDA twin pregnancies, comprising 14 pre‐TTTS and 113 non‐TTTS pregnancies, after exclusions. Scans were collected at a median frame rate of 97 (range, 28–220) Hz. Laser therapy was performed at a median gestational age of 20.6 (range, 17.2–26.6) weeks. There were no group differences in right (RV) or left (LV) ventricular strain discordance between 68/113 non‐TTTS and 13/14 pre‐TTTS MCDA twin pregnancies < 20 completed gestational weeks (RV, P = 0.338; LV, P = 0.932). DVeT% discordance > 3.6% was found in eight of 13 pre‐TTTS pregnancies. In non‐TTTS pregnancies, the estimated variability in ventricular strain within each twin during the day was high (RV, 19.7; LV, 12.9). However, within each pair (intertwin variation), variability was low (RV, 5.5; LV, 2.9). Interclass correlation reflecting the proportion of total variability represented by the variability between twin pairs was low (RV, 0.22; LV, 0.18). Both RV (P < 0.001) and LV (P = 0.025) strain showed a negative association with gestational age. Among non‐TTTS MCDA twin pregnancies, LV strain was, on average, higher by 1.83 in sIUGR compared with normally grown fetuses (P = 0.023), with no statistically significant difference in RV strain (P = 0.271).ConclusionsAlthough ventricular strain has been reported previously as a possible predictor of developing TTTS, in this blinded, prospective study, we found no significant intergroup differences in ventricular strain in pre‐TTTS compared with age‐matched non‐TTTS MCDA twin pregnancies. We recommend using DVeT% discordance as a more practical screening tool in MCDA twin pregnancies. This study also provides new information on the changes with gestational age, and the biological and technical variation, of global longitudinal ventricular strain in uncomplicated MCDA twin pregnancies and those with isolated sIUGR. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Veno–venous anastomoses in twin–twin transfusion syndrome: A multicenter study

IntroductionThe aim of this study is to evaluate the prevalence of veno–venous (VV) anastomoses in a large cohort of monochorionic (MC) twin placentas with twin–twin transfusion syndrome (TTTS) compared to a control group of MC placentas without TTTS. MethodsAll TTTS placentas not treated with fetoscopic laser surgery (TTTS group) and examined at five international fetal therapy centers were included in this study and compared with a control group of MC placentas without TTTS (non-TTTS group). MC placentas were routinely injected with colored dye. We recorded the presence of VV and arterio-arterial (AA) anastomoses. ResultsA total of 414 MC placentas were included in this study (TTTS group, n = 106; non-TTTS group, n = 308). The prevalence of VV anastomoses was significantly higher in the TTTS group than in the non-TTTS group, 36% (38/106) and 25% (78/308), respectively (p = .04; odds ratio (OR) 1.65; 95% confidence interval (CI): 1.03–2.64). In the subgroup of MC placentas without AA anastomoses, the prevalence of VV anastomoses in the TTTS group and non-TTTS group was 32% (18/57) and 8% (2/25), respectively (p = .03; OR: 5.31; 95% CI: 1.13–24.98). DiscussionVV anastomoses are detected more frequently in TTTS placentas than in MC placentas without TTTS and may thus play a role in the development of TTTS.

Duration of the Development of Twin-Twin Transfusion Syndrome

Background: It is generally recommended that monochorionic diamniotic (MD) twin pregnancies be followed by ultrasound examination at least every 2 weeks in order to be able to promptly diagnose twin-twin transfusion syndrome (TTTS). In this study, we retrospectively investigated the clinical significance of TTTS developing at < 2 weeks (n = 9) and ≥ 2 weeks (n = 13). Methods: We examined the following potential factors associated with TTTS development: discordance of the crown-rump length at 8 - 11 weeks, the gestational age at the last confirmation of concordant amniotic fluid (AF), the gestational age at TTTS diagnosis, the estimated fetal weight discordance, and AF values at ≤ 3 - 7 days before TTTS diagnosis. Results: There were no significant differences in these variables between the two groups. Conclusion: There were no significant differences in the clinical histories of TTTS developing at < 2 weeks and ≥ 2 weeks in MD twin pregnancy. J Clin Gynecol Obstet. 2014;3(3):93-96 doi: http://dx.doi.org/10.14740/jcgo270w

Midtrimester isolated polyhydramnios in monochorionic diamniotic multiple gestations

To identify risk factors for development of twin-twin transfusion syndrome (TTTS) in monochorionic diamniotic multiple gestations complicated by midtrimester isolated polyhydramnios (iPoly). A retrospective study of patients referred for possible TTTS between 16 and 26 gestational weeks was performed. IPoly was defined as a maximum vertical pocket of ≥8 cm in the iPoly twin's sac and >2 and <8 cm in the co-twin's sac on the consultative ultrasound. Of 628 consecutive patients referred for possible TTTS, 74were diagnosed with iPoly. The majority of these patients (n= 52, 70.3%) were not subsequently diagnosed with TTTS, and of these, 40were managed expectantly and 12 had amnioreductions because ofsymptomatic iPoly; 30-day perinatal survival of at-least-one twin in thenon-TTTS group was 93.0% (40/43). TTTS developed in the 22 remaining patients, of which 63.6% were of advanced Quintero Stage. Nineteen underwent laser surgery; 30-day perinatal survival of at-least-one twin was 84.2% (16/19). In a multivariate logistic regression model, 2 characteristics were associated with the development of TTTS: (1)gestational age <20 weeks at the time of diagnosis of iPoly (odds ratio, 13.48; 95% confidence interval, 3.40-53.48; P= .0002); and (2) intrauterine growth restriction of the co-twin (odds ratio, 7.28; 95% confidence interval, 1.72-30.88; P= .0071). Among referred patients with midtrimester iPoly, 29.7% subsequently developed TTTS. Early diagnosis (<20 weeks) and/or co-twin intrauterine growth restriction were significant risk factors for development of TTTS in these patients.

The role of veno-venous anastomoses in twin–twin transfusion syndrome

The aim of this study was to investigate the independent role of veno-venous (VV) anastomoses in the development of twin–twin transfusion syndrome (TTTS). Thirty TTTS placentas and 41 non-TTTS placentas, routinely injected with colored dye, were enrolled in this study. We excluded all cases with arterio-arterial (AA) anastomoses and TTTS cases treated with laser surgery. The prevalence of VV anastomoses was significantly higher in TTTS cases compared to non-TTTS cases, 37% (11/30) and 7% (3/41), respectively (P < .01; odds ratio 7.3; 95% confidence interval: 1.8–37.1). Our findings suggest that, in the absence of AA anastomoses, VV anastomoses may enhance the development of TTTS.

Duration of the Development of Twin-Twin Transfusion Syndrome

Duration of the Development of Twin-Twin Transfusion Syndrome

164: Midtrimester isolated polyhydramnios in monochorionic diamniotic multiple gestations

164: Midtrimester isolated polyhydramnios in monochorionic diamniotic multiple gestations

Case-report: Spontanous TAPS detected antenatally in monochorionic twin pregnancy

Introduction: In monochorionic twin pregnancies there might be specific complications, which are due to the single placenta where vascular anastomoses are present. These anastomoses allow the transfer of blood from one fetus to the other and vice versa. They are the course for the development of twin-twin transfusion syndrome (TTTS) and twin anemia-polyzythemia sequence (TAPS). The risk of TTTS is approximately 9% in monochorionic twins. TAPS complicates approximately 3 – 5% of monochoriotic twin pregnancies, whereas the postlaser form occurs in 2 – 13%. Most cases of TAPS are detected after birth. There are only a few cases described which were detected during pregnancy, most of them after laser surgery. Antenatal criterias of TAPS are the abnormalities in Doppler ultrasound of the fetuses. The peak systolic velocity of the middle cerebral artery (MCA-PSV) shows an increase in the donor twin and a decrease in the recipient. The cutoff-levels are 1,5 multiples of median (MoM) for the donor and about 0,8 or 1,0 MoM for the acceptor.

Velamentous cord insertion in monochorionic twins with or without twin–twin transfusion syndrome: Does it matter?

ObjectiveTo study the association between velamentous cord insertion (VCI) and different outcomes in monochorionic twins with and without twin–twin transfusion syndrome (TTTS). MethodsWe recorded the cord insertion type in all consecutive monochorionic placentas examined in two tertiary medical centers. The association between VCI and several outcomes was estimated. ResultsA total of 630 monochorionic placentas with TTTS (n = 304) and without TTTS (n = 326) were studied. The incidence of VCI in the TTTS and non-TTTS group was 36.8% and 35.9%, respectively (P = 0.886). The presence of VCI in one twin was significantly associated with small for gestational age (SGA) status (odds ratio [OR] 1.45, 95% CI 1.13, 1.87) and severe birth weight discordance (OR 3.09, 95% CI 1.93, 4.96). Our results also showed significant interaction between TTTS and VCI when we considered intrauterine fetal demise (IUFD) and gestational age (GA) at birth. The prevalence of IUFD in monochorionic pregnancies without TTTS increased from 4.6% to 14.1% in the presence of VCI (P = 0.027). In the TTTS group, the prevalence of IUFD was comparable in the absence or presence of VCI. Similarly, GA at birth was significantly lower in the presence of VCI only in the non-TTTS group. ConclusionOur findings suggest that VCI is not associated with the development of TTTS but increases the risk of adverse outcomes. Both VCI and TTTS independently increase the prevalence of IUFD and lower GA at birth in a similar way, showing that VCI is an important indicator of adverse perinatal outcome in monochorionic twins.

The prevalence and clinical features of twin-twin transfusion syndrome with onset during the third trimester

To describe the incidence and clinical features of twin-twin transfusion syndrome (TTTS) with third trimester onset. We performed a retrospective chart review of monochorionic diamniotic (MD) twin pregnancies delivered during a recent 4-year period. The inclusion criterion was women who received prenatal care at our center from the first trimester onward. Serial ultrasound examinations were performed at least every 2 weeks until delivery to evaluate fetal growth as well as to estimate amniotic fluid volume. The prevalence of TTTS onset after 28 weeks of gestation and clinical features, including neonatal outcomes and placental findings, were elucidated. Meeting our inclusion criterion were 143 MD twin pregnancies, including 15 TTTS cases (10%). Five cases (4%) developed TTTS during the third trimester and underwent a cesarean section immediately after the diagnosis. All of these women exhibited either abdominal distension or uterine contractions. Recipient twins tended to require more intensive cardiopulmonary treatment than donors, however, neither a recipient nor a donor twin suffered neonatal death or neurological impairment. Placental arterio-arterial anastomoses were detected in three out of five cases. Arteriovenous anastomoses were present in all cases, however, venovenous anastomoses were not found in any case. TTTS is a relatively rare complication during the third trimester. It is imperative to be observant for the development of TTTS in MD twin pregnancies with any abdominal symptoms, even if they appear insignificant.

The Use of Amniotic Fluid Discordance in the Early Second Trimester to Predict Severe Twin-Twin Transfusion Syndrome

Introduction: The appropriate effectiveness of inter-twin amniotic fluid discordance (AFD) in the early second trimester for the prediction of severe twin-twin transfusion syndrome (TTTS) was evaluated. Materials and Methods: The largest AFD between 16 and 18 weeks' gestation was analyzed in correlation with TTTS development defined by polyhydramnios with a maximum vertical pocket (MVP) ≥8 cm combined with oligohydramnios with a MVP ≤2 cm using the receiver operating characteristics curve. All pregnancies were stratified according to an AFD cutoff, and perinatal outcomes were compared between two groups. Results: A total of 223 twin monochorionic pregnancies met the inclusion criteria and 20 patients (8.9%) developed TTTS. An AFD ≥4 cm was calculated to be the optimal point of demarcation to predict subsequent TTTS. The sensitivity and specificity of this AFD cutoff for the development of TTTS were 70 and 97%, respectively. An AFD ≥4 cm was associated with a significantly increased risk of the development of TTTS (70 vs. 2.9%; p < 0.01). Those pregnancies with AFD tended to deliver at an earlier gestational age and were also significantly associated with intrauterine fetal deaths. Discussion: The AFD between monochorionic diamniotic twins in the early second trimester may be useful for the prediction of severe TTTS development.

Placental magnetic resonance imaging in monochorionic twin pregnancies

Objective: Twin-twin transfusion syndrome (TTTS) is a severe complication of monochorionic pregnancies. Placental hydrops might be a marker for TTTS. The purpose of this study was to evaluate whether differences in the placental parenchyma due to TTTS can be seen with fetal MRI. Methods: In a retrospective study, 34 monochorionic pregnancies were investigated on a 1.5 Tesla MR. Seventeen pregnancies were affected by TTTS, and 17 showed no clinical signs of TTTS. Placental maturation and vascular pathologies, as well as the extent of the placental findings and allocation of placental tissue to each twin, were investigated. Placental findings were reported for origin, size, maturation, and placental thickness, and were correlated with the presence of TTTS. Results: All placentas affected by TTTS showed abnormal maturation on MR scans, but only 64.7% of the non-TTTS group (p = 0.018). Vascular placental pathologies did not differ significantly between the TTTS and non-TTTS group. Conclusions: MR-signs of placental maturity in monochorionic twin pregnancies may indicate a lower risk of development of TTTS.

Maternal weight gain in twin–twin transfusion syndrome

To examine the association between maternal weight gain and twin-twin transfusion syndrome (TTTS). Retrospective observational study in two tertiary care centers. All 124 women with monochorionic diamniotic twin pregnancies who gave birth at ≥ 16 gestational weeks between 2002 and 2010. Analysis of chronological relation between maternal weight gain per week (weekly gain) and the diagnosis of TTTS. Sonographic diagnosis of TTTS. A weekly weight gain ≥ 1.4 kg occurred in 45 women, preceded the diagnosis of TTTS in 22 (78.6%) of the 28 women with TTTS, and was associated with TTTS [women with one weekly weight gain ≥ 1.4 kg vs. women with no weekly weight gains ≥1.4 kg who were diagnosed as having TTTS: 48.9% (22/45) vs. 7.6% (6/79); RR, 6.44; 95%CI, 2.82-14.69]. At given gestational weeks between 16 and 27, the mean (± SD) prospective risk of the development of TTTS within three weeks was 52.0 ± 33.8% among women who showed a weekly weight gain ≥ 1.4 kg for the first time, whereas the risk of the development of TTTS within one week was 1.6 ± 1.7% among women who never showed a weekly weight gain ≥ 1.4 kg. Excessive maternal weight gain ≥ 1.4 kg/week is likely to occur during the development of TTTS.

Monochorionic Diamniotic Twin Pregnancy

Twin-twin transfusion syndrome complicates up to 15% of monochorionic diamniotic gestations. Current recommendations for sonographic surveillance in monochorionic diamniotic pregnancies for detection of twin-twin transfusion syndrome vary. Our objective was to determine an appropriate frequency of sonographic surveillance to optimize detection of twin-twin transfusion syndrome in monochorionic diamniotic gestations. A retrospective cohort analysis of all nonanomalous monochorionic diamniotic twins delivered at the University of North Carolina over a 9-year period was performed. The rate and gestational age of twin-twin transfusion syndrome onset were calculated. The time to the diagnosis of twin-twin transfusion syndrome was evaluated by a Kaplan-Meier survival curve; clinical factors at initial sonography were examined for their use in prediction of twin-twin transfusion syndrome. Of the 577 twin deliveries, 145 (25%) were monochorionic diamniotic and included for analysis. The rate of twin-twin transfusion syndrome was 17.93% (n = 26). The mean frequency of surveillance ± SD before diagnosis of twin-twin transfusion syndrome was 3.1 ± 2.1 weeks. The mean gestational age at diagnosis of twin-twin transfusion syndrome was 21.3 ± 3.4 weeks (range, 15-29 weeks). Both a discordant maximum vertical amniotic fluid pocket (>65% difference) and a discordant estimated fetal weight (>25% difference) at initial sonography showed a significantly shorter time to diagnosis of twin-twin transfusion syndrome (P < .0001). Evaluation for twin-twin transfusion syndrome should begin in the second trimester. Weekly surveillance for those pregnancies with estimated fetal weight or maximum vertical pocket discordance is recommended. For those with a concordant estimated fetal weight and maximum vertical pocket, sonographic evaluation every 2 weeks is warranted to 28 to 30 weeks. After that, development of twin-twin transfusion syndrome is less likely, and a different paradigm of antenatal testing may be reasonable.

Residual Vascular Communications in Twin-twin Transfusion Syndrome Treated With Sequential Laser Surgery: Frequency and Clinical Implications

Unbalanced sharing of blood through vascular communications in the common placenta is thought to be responsible for the development of twin-twin transfusion syndrome (TTTS) in monochorionic diamniotic twins. Fetoscopic laser surgery treats TTTS in utero by ablating placental vascular communications. The resulting separation of the fetal circulatory systems improves perinatal survival and neurological outcome. Several studies have demonstrated that, after laser surgery, residual vascular communications (RVC) may be present in up to one-third of cases, and may be associated with persistent TTTS or twin anemia-polycythemia sequence (TAPS) and other adverse perinatal outcomes. A wide range of RVC rates (from 32% to 75% of cases) have been reported in similar patient populations. This variability in RVC rates has been attributed to the laser technique used and the method of placental evaluation. The primary aim of this study was to determine the frequency of residual RVC in a large series of placentas treated in utero for TTTS using preferential sequential selective laser photocoagulation of communicating vessels. A secondary aim was to investigate potential clinical risk factors associated with RVC and perinatal outcomes of cases complicated by RVC. The study subjects were pregnant women who underwent preferential sequential selective laser photocoagulation of communicating vessels for TTTS from 2006 through 2009 at an academic medical center. After delivery, placentas were submitted for examination and water and/or milk injections were used to assess the patency of vascular communications between the twins. Cases with placental disruption and intrauterine fetal demise were excluded from the analysis. Perinatal outcomes of cases with and without RVC were compared. Over the 3 years of the study, 174 women with TTTS were treated by preferential sequential selective laser photocoagulation of communicating vessels. Of the 174 cases, 133 (76%) resulted in survival of both twins at birth, and 105 (79%) of these submitted an intact placenta for pathological evaluation. Injection studies showed the presence of RVC in 5 of the 105 placentas (4.8%). One of the 5 RVC cases (20%) had neonatal findings consistent with TAPS, whereas none of the no-RVC cases had TAPS. There was one case of persistent TTTS in the no-RVC group. The gestational age, estimated fetal weights, and amniotic fluid volumes in each sac at the time of the procedure were similar in RVC and no-RVC cases. There was a trend toward a longer operative time in RVC cases (63.4 vs. 44.4 min; P = 0.057), but this did not reach statistical significance. Outcomes of RVC and no-RVC cases were also similar: gestational age at delivery = 28.7 ± 6.5 versus 33.4 ± 3.3 weeks (P = 0.178), and donor birth weight = 1429 ± 1369 versus 1653 ± 715 g (P = 0.518). The only differences between the groups were that the no-RVC group had a higher recipient birth weight (1287 ± 1061 vs. 1973 ± 610 g; P = 0.020), and the donor in the RVC cases was more likely to have central or eccentric placental cord insertion (80% vs. 17%; P = 0.006). No histological differences were found between the placentas with and without RVC. These findings show that the frequency of RVC among gestations with dual survivors after preferential sequential selective laser photocoagulation of communicating vessels treatment for TTTS was less than 5%.

Nuchal translucency thickness and crown rump length discordance for the prediction of outcome in monochorionic diamniotic pregnancies

Background Ultrasonographic features of the underlying hemodynamic changes in twin–twin transfusion syndrome (TTTS) may be present at the first trimester scan. Aims To investigate the value of intertwin discordance in nuchal translucency (NT) thickness and crown rump length (CRL) to predict TTTS and other adverse outcomes. Study design Cohort study. Subjects One hundred and thirty-five unselected consecutive monochorionic diamniotic twin pregnancies. Outcome measures NT and CRL discordance were assessed at 11 to 13 + 6 weeks' gestation. Receiver–operating characteristics (ROC) curves were used to determine their predictive ability for the subsequent development of TTTS. Results TTTS complicated 16/135 (12%) pregnancies. Four other pregnancies were complicated by selective intrauterine growth restriction (sIUGR) and 3 by miscarriage < 24 weeks gestation. The median NT discordance was 15% (range 0–37%) in TTTS pregnancies, 13% (12–19%) in those with miscarriage < 24 weeks’ gestation, 47% (30–50%) in those with sIUGR, and 14% (0–86%) in those without complications. Prediction for subsequent development of TTTS provided by the discordance in CRL, expressed as the area under ROC curve, was 0.52 (95% confidence interval 0.38–0.67), while it was 0.50 for NT discordance (95% confidence interval 0.35–0.64). NT discordance was significantly higher in sIUGR compared to both uncomplicated and TTTS pregnancies (p = 0.004 and p = 0.003, respectively). Conclusion In an unselected population of monochorionic twin pregnancies, discordance in CRL and NT measured during first trimester scan is not a clinically useful predictor of the subsequent development of TTTS. Therefore, strict ultrasound follow up is recommended for the timely diagnosis of TTTS.

Screening for twin–twin transfusion syndrome at 11–14 weeks of pregnancy: the key role of ductus venosus blood flow assessment

A discrepancy in crown-rump length (CRL) and/or nuchal translucency thickness (NT) between monochorionic twins has been found to be associated with an increased risk of twin-twin transfusion syndrome (TTTS). As one of the most plausible mechanisms for increased NT is hemodynamic imbalance and cardiac dysfunction, indirectly manifested by abnormal blood flow in the ductus venosus (DV), we aimed to clarify the role of DV blood flow assessment in identifying those monochorionic twins more prone to develop TTTS. We present 99 cases of monochorionic diamniotic twin pregnancies in which CRL, NT and DV blood flow were evaluated at 11-14 weeks' gestation. Discrepant values of CRL were not predictive of TTTS development. Intertwin NT discrepancy >or= 0.6 mm had a sensitivity of 50.0% and a specificity of 92.0%. The presence of at least one abnormal blood flow waveform in the DV was associated with a relative risk for developing TTTS of 11.86 (95% CI, 3.05-57.45), with a sensitivity of 75.0% and a specificity of 92.0%. The combination of abnormal DV blood flow with NT discrepancy >or= 0.6 mm yielded a relative risk for the development of TTTS of 21 (95% CI, 5.47-98.33). Both intertwin discrepancy in NT and abnormal flow in the DV in monochorionic twins may represent early manifestations of hemodynamic imbalance between donor and recipient. In these pregnancies, in addition to NT measurement at 11-14 weeks, the Doppler assessment of DV blood flow significantly increases the performance of screening for those at risk of developing TTTS.

Nuchal Translucency Thickness in Monochorionic Multiple Pregnancies

The purpose of this study was to investigate the value of first-trimester nuchal translucency (NT) thickness in predicting the pregnancy outcome in monochorionic multiple pregnancies. Thirty monochorionic multiple pregnancies were evaluated for NT thickness at a median gestational age of 12 weeks (range, 11-14 weeks). Information on pregnancy outcome was obtained from all cases. A poor pregnancy outcome was defined as fetal death or miscarriage before 24 weeks, development of twin-twin transfusion syndrome (TTTS), or preterm delivery before 32 weeks. The NT thickness was above the 95th percentile for gestational age in at least 1 fetus in 5 (17%) pregnancies, and a poor pregnancy outcome was recorded in 14 (47%) pregnancies. The overall sensitivity was 36% (5/14); specificity, 100% (16/16); positive predictive value, 100% (5/5); and negative predictive value, 64% (16/25). In pregnancies with increased compared with normal NT thickness, no significant correlation was found with the subsequent development of TTTS (1/5 [20%] versus 5/25 [20%]) and miscarriage or fetal death before 24 weeks (1/5 [20%] versus 3/25 [12%]). However, among the 20 pregnancies not complicated by TTTS or loss before 24 weeks, there was a significantly increased rate of delivery before 32 weeks in the former group (3/4 [75%] versus 1/16 [6.3%]; P = .01). In monochorionic multiple pregnancies, an increased NT thickness measurement had a high specificity and positive predictive value for adverse perinatal outcomes. However, the sensitivity and negative predictive value were low, with a normal NT thickness measurement poorly predicting development of complications; therefore, close sonographic follow-up should be carried out in all cases, irrespective of NT thickness.